(a) Field of the Invention
The present invention relates to a process for reclaiming salvaged asphalt, more particularly to an asphalt reclaiming process in which the salvaged asphalt is heated indirectly, the heat being regenerated to perform secondary heating, and is mixed with new sands, stones and tar added in a designed proportion.
(b) Description of the Prior Art
In conventional processes for making asphalt and for reclaiming salvaged asphalt, two sets of costly equipment and complicated processing steps have to be employed. The process for reclaiming salvaged asphalt is even more complicated.. The conventional processes for making asphalt and for reclaiming salvaged asphalt are briefly described as follows:
(1) In the conventional asphalt making process, the steps include feeding, direct heating, screening, and mixing with tar. In the step of direct heating, a burner 11 disposed inside a drying machine 1 (see FIG. 1) has to be fired to about 1200xc2x0 C. in order to instantly heat the mixture of stones and sands to above 155xc2x0 C. and, after screening, mix it with tar. The internal structure of the drying machine 1 is a single-layer gyroscopic drum 12. The body of the burner 11 is a piece of complicated high heat efficiency machinery, which is costly, and the heat released thereby is high. However, the released heat cannot be regenerated, and the waste gas thus produced is relatively considerable and should be appropriately controlled so as not to create air pollution.
(2) In the conventional process for reclaiming salvaged asphalt, the steps include feeding, indirect heating, and mixing proportionally with new asphalt product. In the indirect heating step, a drying machine 2 (see FIG. 2) is used. The interior of the drying machine 2 is also a single-layer gyroscopic drum 23 having a hot air generating machine 22 connected to a burner 21. The temperature generated can only heat the salvaged asphalt to below 80xc2x0 C., and is unable to heat the salvaged asphalt mixed with stones and sands to a normal temperature of about 155xc2x0 C. Even if 155xc2x0 C. can be attained, the residual tar content in the salvaged asphalt will reach its burning point and start burning. This is the reason why indirect heating is used. The rate of reclamation of salvaged asphalt to form reclaimed asphalt product using the above-described conventional process is only 30%xcx9c50%, which is very low. Besides, the salvaged asphalt has to be proportioned with new asphalt product before mixing therewith. In more concrete terms, in asphalt reclamation projects, two sets of equipment, one for making new asphalt product, the other for reclaiming salvaged asphalt, have to be used, which is especially costly in view of the low reclamation rate. Besides, the quality of the reclaimed asphalt product is inferior to that of new asphalt product. How to enhance the asphalt reclamation rate and the quality of the reclaimed product while lowering manufacturing costs and simplifying the process steps as well as avoiding environmental pollution is the major topic the present invention aims to study.
A primary object of the present invention is to provide a process for reclaiming salvaged asphalt including the steps of feeding salvaged asphalt mixed with new sands, stones and tar in a designed proportion into a double-layer drying machine including inner and outer gyroscopic drums; indirectly heating the salvaged asphalt in the drying machine by using a plurality of burners disposed externally to dry the salvaged asphalt, the heat thus generated being recycled via a draft tube into the drying machine to further heat the salvaged asphalt until the tar in the mixture starts to soften at about 80xc2x0 C.; and mixing the salvaged asphalt with tar to form rejuvenated asphalt product when they travel to the outer gyroscopic drum in which the temperature reaches and the temperature of the stones contained in the salvaged asphalt also reaches a temperature of 160xc2x0 C. for fusion with the tar.
Another object of the present invention is to provide a process for reclaiming salvaged asphalt, in which the heat generated by the burners are recycled via a draft tube into the double-layer drying machine so that the burners do not need to perform instant heating. Recycling of the heat energy assists the burners to attain the temperature required to reclaim salvaged asphalt. By virtue of the process of the present invention, equipment costs can be reduced; the rate of asphalt reclamation can be raised to 100%; the quality of the rejuvenated asphalt product is satisfactory; and environmental requirements can also be met.